Key term
OCR GCSE Chemistry A J248
Chemical Reactions
Topic overviewWriting formulae of elements and compoundsBalanced equations, and deducing formulae from ionsState symbols in equationsConservation of mass, and changes of mass in open systemsExothermic and endothermic reactions, and reaction profilesActivation energy and why reactions need itOxidation and reduction in terms of oxygenAcids, alkalis and neutralisationThe ionic equation for neutralisation, and reactions of acidsThe pH scale, acidity and alkalinityMeasuring pH with indicators and pH metersProducts at the electrodes, and molten ionic compoundsElectrolysis of aqueous solutionsInert and non-inert electrodes
Elements, Compounds and Mixtures
Topic overviewPurity, and melting point dataRelative formula mass and empirical formulaeFormulations, and separating mixturesPaper and thin layer chromatographyInterpreting chromatograms and Rf valuesChoosing a purification methodMetals and non-metals in the Periodic TableElectron arrangement and position in the Periodic TableIonic, covalent and metallic bonding comparedDot and cross diagrams, and the limits of modelsReactions, electron arrangement and Mendeleev's tableCarbon's four bonds, and the variety of organic compoundsDiamond, graphite, fullerenes and grapheneBond strength, intermolecular forces and predicting stateBulk properties of ionic, molecular and giant structuresNanoparticles: size and surface area to volumeUses and risks of nanoparticulate materials
Global Challenges
Topic overviewExtracting metals by reduction and by electrolysisThe Haber process and fertiliser productionNitrogen, phosphorus and potassium in agricultureLife cycle assessmentRecycling, and the decisions behind itAlloys, and the corrosion of metalsComparing glass, ceramics, polymers, composites and metalsFunctional groups and homologous seriesPredicting the products of organic reactionsAddition polymerisationDNA and other natural polymersFractional distillation of crude oilThe fractions, and crude oil as a feedstockDependence on hydrocarbons, and crackingChemical cells and fuel cellsThe Earth's early atmosphere, and how oxygen developedThe greenhouse effect, and evidence for climate changeEffects of carbon dioxide and methane, and air pollutantsProducing potable water
Monitoring and Controlling Chemical Reactions
Topic overviewCarrying out an acid–alkali titrationTheoretical mass and percentage yieldAtom economy and its calculationMeasuring the rate of a reaction, and rate graphsFactors affecting rate, and collision theorySurface area and rateCatalysts and how they workReversible reactions and dynamic equilibriumActivation energy, and enzymes as catalysts
Particles
Predicting and Identifying Reactions
Topic overviewGroups 1, 7 and 0, and why they behave as they doTransition metalsPredicting reactivity from the Periodic TableReactivity of metals with water and acidsTests for oxygen, hydrogen, carbon dioxide and chlorineTests for aqueous cations and anionsFlame tests, and identifying metal ionsIdentifying a species from test resultsInstrumental methods of analysis
Global Challenges
Effects of carbon dioxide and methane, and air pollutants
- 2 things to know
- Paper 2
Overview
The effects of rising carbon dioxide and methane such as warming and rising sea levels, sources of methane, ways to cut emissions including carbon capture and storage and planting trees, why global action is hard, the sources and harm of carbon monoxide, sulfur dioxide, oxides of nitrogen and particulates, and presenting and sampling pollution data with bar charts, histograms and frequency tables.
What you need to know
Answer each one before you reveal it.
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Key term
Why is a rise in sea level a serious risk?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Give two potential effects on the Earth of rising levels of carbon dioxide and methane.
Model answer
A rise in average global temperature, and melting of polar ice leading to rising sea levels.
- 2
Why is a rise in sea level a serious risk?
Model answer
Low-lying land floods, so homes, farmland and coastal habitats are lost.
- 3
Give two human activities that release methane into the atmosphere.
Model answer
Keeping cattle and growing rice in flooded paddies, together with rotting waste in landfill sites and leaks from gas extraction.
- 4
How does methane compare with carbon dioxide as a greenhouse gas?
Model answer
Each methane molecule traps far more infrared radiation than a molecule of carbon dioxide, but there is much less of it in the atmosphere.
- 5
Give three ways of reducing carbon dioxide emissions.
Model answer
Generate electricity from renewable or nuclear sources instead of fossil fuels, make transport and buildings more efficient, and capture and store the carbon dioxide from power stations.
- 6
What is carbon capture and storage?
Model answer
Carbon dioxide is removed from the waste gases of a power station and pumped into rock formations deep underground so that it does not reach the atmosphere.
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